A projection-type image display device such as a liquid crystal projector irradiates light emitted from a light source such as a mercury lamp onto a display element such as a liquid crystal panel and magnifies and projects the image formed on the display element from a projection lens to a screen or the like. An optical system of the device includes an optical unit (hereinafter, referred to as an optical engine) used to form an image by irradiating light emitted from a light source onto a liquid crystal panel and a projection optical system that magnifies and projects the image formed on the liquid crystal panel using the projection lens.
The projection optical system is provided with a lens shift mechanism for shifting the projection lens perpendicularly to an optical axis in order to adjust an image display position on the screen. The lens shift mechanism shifts the projection lens in two directions perpendicular to the optical axis of the projection light, that is, horizontal and vertical directions, so that improved operability is necessary. Patent Document 1 proposes a mechanism capable of allowing a user to easily recognize a shift direction of the projection optical system by aligning a shift direction and an operation knob direction of the projection optical system in order to improve operability.